A co-inventor and myself have shown how to inject a pressurized fuel vapor/steam mixture into the cylinder of a piston engine. German Patent Disclosure DE-OS 37 34 346, corresponding to U.S. Pat. No. 4,909,192, discloses generating the fuel vapor/steam mixture using the heat contained in exhaust gases, and, without first mixing with combustion air, feeding the mixture directly from a vapor mixture generator to the cylinder. The fuel vapor/steam mixture is fed into pre-compressed combustion air during the compression stroke of the piston engine and is subsequently ignited in the cylinder.
The pressure necessary for injection is generated in the fuel vapor/steam mixture by supply pumps, which respectively feed the water and the liquid fuel to the vapor mixture generator.
It is significant how the feeding of the necessary fuel vapor/steam mixture is controlled. According to the known method, the pressure of the fuel vapor/steam mixture is set higher than the maximal compression pressure in the cylinder. For mixture regulation, given the variety of engine capacities and engine RPM's, a heavy investment in controls is needed, due to the need to match the opening times of the injection valves. Further, due to the high required pressure in the fuel vapor/steam mixture, the generation of the mixture becomes problematical. As pressure increases, the temperature needed for fuel vaporization increases, and when one increases the temperature in a vaporizer, one has to expect formation from the fuel of cokes and other unvaporizable fractions.